Piston-ring.



M. L. DUNHAM.

PISTON RING.

APPLICATION FILED APn. I8. 1916.

1,241,837. Patented Oct. 2,1917. ay- 2 5 52 iy-i #5 1 UNITED STATlESPATENT OFFICE,

MILLABD L. DUNHAM, 0F YORK, N. Y., ASSIGNOR OF ONE-FOURTH TO LOUIS m: I.HUNGER, OF NEW YORK, N. Y.

Specification of Letters Patent.

Patented Oct. 2, 1917.

Application flied April 18, 1916. Serial No. 81,857.

- in rings produced from circular blanks which are normally oversize,whereby when said rings are contracted in use they are of 4 truecylindrical contour.

Piston rings are usually made from cast iron, and rely for their outwardtension, whereby gas tight relationship with the cylinder wall isprovided, upon the inherent elasticity of the material from which cast,in the restoratory effort toward resumption of their original contour;after the inward compression to which they must be subjected in order tointroduce the rings, upon a piston, within the cylinder. Thus the ringsare usually cast of a diameter greater than the inside diameter of thecylinder with which they are to be used, and are split at one point, bythe removal of a portion of the ring material, leaving two opposed ends,to provide space for the aforesaid inward compression; the. space beingof such extent only that when abridged by the inward compression forservice, the opposed ends will have spaced relationship ust suflicientto serve the purposes of heat expansion and contraction in use.

Under this ordinary method of piston ring manufacture the true circularform becomes distorted when the ring is contracted to fit within thecylinder; the distortion consisting in portions of the ring, near itsends, lagging inwardly, leaving clearances between the outer peripheralsurface of said p0rtionsover certain arcsand the opposed portions of thecylinder wall. These clearances permit suflicient leakage to afiect thecylinder compression.

Various means have been sought to rectify this deficiency in istonrings, and my present invention is directed to a circular ring, producedin theordinary way, and treated in a novel, simple and eflicaciousmanner, whereby it is caused to have a true circular contour after ithas been contracted to'fit within a cylinder.

This treatment, in brief, consists in first cutting a piece out of acast ring, iii-the usual vmanner, leaving opposed, separated ends; andthen in spreading themass of the ring material at its outer peripheralsurface, in portions-thereof adjacent to each of its opposed ends; tothereby give those portions, equally, an inherent, inward inclination;which constitutes, in the free state of the rin a distortion thereoffrom a true circle; ut which, in the contracted state of the ring, forservice, gives it an absolutely true circular contour; whereby theclearances before referred to as existing between the ring portions,near their ends, and the cylinder wall, are entirely filled.

Spreading the mass of the ring material, on the outer surface thereof,in its portions toward the ring ends, has the effect of drawing the endportions of the ring inwardly, to give them equally a distorted contour,wherein the ends aforesaid are inclined inwardly, and said end portionscaused to describe a segment of a circle whose diameter is slightly lessthan the diameter of the untreated portion of the ringin its free state.This'may be accomplished by punching indentations in the outerperipheral surface of the ring, over longitudinal portions there ofincluding the ring ends and sections anterior thereto; thecircumferential ring portions, thus defined, comprising the arcsreferred to in which leakage clearances exist under the presentconstruction of piston rings.

The mass spreading, as by punching of indentations aforesaid, has theeffect of drawing inwardly the ring end portions, to thus slightlydistort the ring in its free state; but causing it to have a truecylindrical contour when contracted in service. The stated result isachieved without detraction from the inherent elasticity of the ringmaterial; the ring, after treatment, functioning as before; with theexception that, on account of its treatment, it is enabled to fit snuglywithin a cylinder, without leaving any clearance spaces.

ating with the heel of the ring as a fulcrum,

Fig. 2 is an edge view thereof, showing the method of formingindentations therein to spread the mass of the material.

Fig. 3 is a plan view,- showing the effect of the mass spreadin inchanging the ring contour at one side 0 the spacing.

. Fig. 4=is a similar view, showing the ring as treated in Fig. 3, tofit within a cylinder.

Fig. 5 is an enlarged detail view, showing the nu as treated at bothsides of the spacing an contracted to fit within a cylinder,

and.

gree of outward tension. The fault in this general form of ringconstruction, as now practised, is that while the diameter of the ring,in a line drawn through its joint and heel, ,will remain practicallyunchanged when contracted, the side portions of the ring, nearthe joint,will then sag inwardly,

when contracted, leaving at those points leakage spaces between the ringand cylinder. This defect is remedied by me by distorting the ring fromits circular condition shown in Fig. 1, through a certain treatment-which results in causin the ring ends 2, 3,

and portions adjacent thereto to incline inwardly, having the efiect,when the ring is contracted, to bring. its. ends together, of thencausing the ring to assume a true circular form.

Fig. 2 illustrates the. character of the treatment applied, which isthat of punching indentations, as 4, in the outer perpiheral surface ofthe ring, along restricted pormama:

tions thereof lying between the ring ends and a medial line awn acrossthe ring, be tween its joint and heel.

Said indentations are roduced by a tool,

as 5, and serve to slight y spread the mass 7 of the rin material atthose portions, which has the e ect of giving the ringa permanentdistortion in its free state, as stated, which distortion enables thering to assume an absolutely true circular form when contracted.

, Reference to Fig. 3 will show one side'only of the ring as treated,the treated side 5, in the free state of the ring being distorted, whilethe opposite side 6 remains of circular form. In further illustration ofthe effect thus obtained, I have shown, in Fig. 4, the partly treatedring of Fig. 3 as contracted and placed within a cylinder 7. It willthere be seen thatthe treated portion of the ring, as contracted, fitsperfectly within the cylinder 7, the opposite, untreated side 6 of the rng appearing as distortedin the contracted state, whereby a clearance isseen to exist between said portion 6 and the cylinder wall. The efficapyof this treatment, as applied to both portions 5 and 6 of the ring, isclearly shown in Fig. 5, where the ring is seen to fit closely withinthe cylinder.

' Attention is directed to my co-pending application, Serial No. 91856,filed April 18, 1916, for a method of producing improved piston rings,which is the sub ect of this application. 7

Variations may be resorted to within the spirit and scope of myinvention.

I claim:

A piston ring consisting of a separated, circular metal ring, whosenormal diameter exceeds the inside diameter of the cylinder with whichused, said ring having the mass of its outer peripheral materialdisplaced 'at the end portions of the ring, giving said end portions aninward inclination, whereby the ring, when contracted in use, is of truecircular form.

- Signed at the borough of Manhattan in the city, county and State ofNew York this 14th day of April A; D. 1916.

MILLARD L. DUNHAM.

itnesses:

W. E. FEE, F. W. BARKER.

